Ever since the first integrated circuit was demonstrated, one goal of the electronics industry has been to increase the density of individual devices in an integrated circuit. Ultimately, as smaller devices are made, the devices can be packed more densely, which reduces transmission between devices and also allows for faster operation.
Metal oxide semiconductor (MOS) technology forms the basis for a large part of chip manufacturing. In typical MOS transistor technology, silicon dioxide (SiO2) is grown on a silicon substrate so as to form part of a metal oxide semiconductor gate. SiO2 so formed is commonly referred to as a gate oxide or a gate oxide dielectric. Until recently, SiO2 grown on MOS transistor gates has always been thought of as amorphous with little ordering in the first atomic layers at the interface between the silicon substrate and the oxide layer. Silicon has been used commercially as a semiconductor preferentially over other materials because it readily forms stable oxide dielectric layers with a lower interface defect density than other semiconductors and their oxides. The stability of Si/SiO2 having a low interface defect density enables the manufacture of transistors with better electrical properties than is attainable with other semiconductors.
The desire for lower dimension devices presents a basic problem: as devices get smaller in three dimensions, the dielectric layer must get both narrower and thinner and continue to function as a dielectric. Silicon does not always provide the optimum physical and electronic properties, such as a low interface defect density or a high dielectric constant, necessary to or tailored to fill a particular need. A desire for materials that have better tailored physical and electronic properties creates another problem: growth of dielectric layers on multi-element semiconductors is difficult. These two problems become essentially insurmountable when one desires a small device made out of a semiconductor other than doped silicon. Conceptually, a solution would lie in producing either a well-ordered ultra-thin oxide on top of the multi-element semiconductor, or at least a more ordered interface between the semiconductor and the dielectric layers. Doing so without elemental or phase separation is extremely difficult especially in chemical systems where the defect generation rate is higher than silicon, and as the physical sizes involved approach atomic dimensions. Any improvement in ordering at the interface or in the material will improve the interface defect density. It will be appreciated that, as smaller devices demand thinner dielectric layers, interface characteristics become increasingly important.
Another goal of electronic device processing is the growth of heterodielectrics or other materials listed below on a semiconductor substrate. While this goal is achievable for some systems, in general, growth of ordered films of a material on a semiconductor substrate is difficult. U.S. Pat. No. 6,613,677, incorporated herein by reference, discloses long range ordered semiconductor interface phase and oxides that can improve many properties of oxides, and in particular SiO2 grown on Si. However, the growth of epitaxial, or continuous crystalline films on semiconductor substrates remains elusive. Herein, are described novel methods for preparing semiconductor substrates and forming epitaxial interfacial layers of oxides thereon.